A. Field of the Invention
This invention relates generally to the field of devices used to measure and display bio-potential signals generated by the body. More particularly, the invention relates to a plurality of wireless, remotely programmable electrode transceiver assemblies that are each coupled to a conventional patch electrode, and an associated base unit. The base unit obtains a patient""s electrocardiogram (ECG) or other bio-potential signal from the wireless transceivers and supplies the signal to a monitor unit for display. The display may be a standard ECG monitor.
B. Statement of Related Art
Conventional ECG apparatus for hospital bedside monitoring typically requires up to ten wired electrodes. Each electrode is attached to the body of the patient, and has a wire, several feet or more in length, leading to an ECG monitor. Such electrodes are used to detect heart signals from the patient and convert them into a multiple-lead ECG evaluation.
The lengthy wired electrodes of conventional ECG apparatus obstruct the patient and limit the patient""s freedom of movement. They are also cumbersome for the physician or assisting nurse. Telemetry systems for wireless ECG monitoring for patients in hospitals currently exist. These systems are more expensive, intended for greater range (higher power), and do not totally eliminate the physical electrode wires attached to the patient. Instead of being connected to the monitor, the electrodes are each wired to a single transmitter box that is worn by the patient. Some telemetry systems also may not handle a 12 lead ECG (10 wires) because of the wiring that is required between the electrodes and the transmitter box. For example, the Spacelabs Ultraview Modular Digital Telemetry system can only handle a maximum of four leads (5 wires).
Wireless medical monitoring and diagnosis systems have been proposed in the prior art. U.S. Pat. No. 5,862,803 to Besson et al. describes a wireless electrode/sensor patch system with sensor, controller and transceiver electronics contained in an electrode patch assembly. U.S. Pat. Nos. 5,307,818, 5,168,814 and 4,981,141, all issued to Segalowitz, describe a wireless electrode system for ECG monitoring. The Besson et al. and Segalowitz patents are incorporated by reference herein. The Segalowitz patents describe a single piece electrode patch with built-in microchips for wireless one way communication, and a snap on electronic-assembly that fastens to a disposable electrode patch. However, the electrode patch is a special two-conductor type that is not conventional. The electrode assemblies are either transmit only or receive only (not both). A reference signal (generated from a Wilson network) is transmitted from the base unit to only the Right Leg electrode patch, which is receive only. Electrodes can only be programmed via manual switches on the electrode casing, not over-the-air from the base unit. For the multiple electrode embodiment, the base unit contains multiple receivers and antennas which imply multiple transmit frequencies are required for the system and over-the-air signaling (thus making the base unit more costly to implement). There is no mention of error correction or detection capability in the electrodes or base unit.
In another embodiment of the Segalowitz ""818 patent, there is discussion of a single strip assembly which contains all of the electrodes required for 12-lead ECG monitoring with microchip circuitry contained in the strip assembly (not in the individual electrode patches). In this configuration, the ECG signals from each electrode are multiplexed and transmitted from a single transmitter (contained in the strip assembly) via time multiplexing on a single digitally encoded frequency channel. However, no time multiplexing on a single frequency channel is discussed for their multiple transmit electrode embodiment, as discussed in the present invention.
The present invention is not intended to replace existing telemetry systems, but rather to provide a more convenient and cost effective solution for low power wireless ECG monitoring, in a hospital room environment, without having to replace the hospital""s existing ECG bedside monitoring equipment. Furthermore, the present invention provides for programmable features by which a base unit can remotely program multiple wireless transceivers. This provides greater flexibility and customization of a wireless ECG acquisition system. As such, it is believed to be an improvement to the systems proposed by Besson et al. and Segalowitz.
In a first aspect, a wireless electrocardiogram (ECG) acquisition system is provided. The system includes a plurality of individual, remotely programmable wireless transceivers, each of which are associated with a patch electrode for use in ECG monitoring. The patch electrodes are of conventional design and adapted to be placed on the surface of the patient""s body for measuring electrical potentials. The system further includes a base unit comprising a wireless transceiver for sending and receiving messages to the plurality of individual wireless transceivers. The messages include configuration commands for the plurality of individual transceivers. Examples of the configuration commands include data acquisition commands, transmission control commands, such as frequency selection commands, and other commands described in further detail below.
The base unit, in accordance with this first aspect of the invention, transmits a global time base signal to the plurality of individual wireless transceivers. The global time base signal is used for synchronizing the timing of transmission of signals acquired by the individual wireless transceivers to the base unit in discrete time slots in a single frequency channel. This time division multiplexing provides that each wireless transceiver transmits its signals to the base unit in discrete time slots, with the wireless transceivers sharing a common channel.
The base unit has an interface to an ECG monitor for display and analysis by the user. Preferably, the ECG monitor is a conventional, standard monitor typically used today in the hospital setting. The ECG signals are provided by the base unit to the monitor in a fashion that is transparent to the monitor, i.e., the data is formatted and provided in a form whereby the monitor cannot distinguish the signals from conventional, wired electrode input signals. The ECG monitor preferably accepts the individual electrode signals in order to develop any required lead configuration.
In a preferred embodiment, the wireless two-way communication between the base unit and the plurality of remotely programmable wireless transceivers is established in accordance with a protocol that provides for transmission of a variety of configuration commands. Examples of such commands include registration information, data acquisition control commands (such as start and stop messages), transmission frequency commands, time slot commands, amplifier gain commands, transmitter control commands, power saving mode commands, initialization commands, and so forth. The ability to remotely program the wireless transceivers gives considerable flexibility over how the electrodes are configured and positioned on the patient""s body.
The plurality of individual wireless transceivers could be designed to be installed on particular locations of the patient""s body, such as left arm, right arm, left leg, etc. In a more preferred embodiment, the individual wireless transceivers are generic with respect to particular placement locations on the surface of a patient""s body. The base unit transmits programming data to the individual wireless transceivers. The programming data includes electrode position location data associated with a unique placement position to be assigned to the individual wireless transceivers, as well as electrode identification data. When the data is acquired from each of the wireless transceivers, the electrode identification data, electrode position location data and the acquired electrode signal are sent from the wireless transceivers to the base unit.
In another aspect of the invention, a dynamically programmable, wireless electrocardiograph (ECG) acquisition system is provided. The system comprises a plurality of individual, remotely programmable wireless transceivers, each transceiver associated with a patch electrode for use in ECG monitoring, and a base unit comprising a wireless transceiver for sending and receiving messages (e.g., commands) to the plurality of individual wireless transceivers. The base unit and the plurality of individual wireless transceivers implement a wireless programming protocol by which information and commands are exchanged between the base unit and individual wireless transceivers. Registration, configuration, and data transmission control properties of the individual wireless transceivers are managed dynamically by the base unit.
As an example of the information that can be transmitted between the base unit and the transceivers, the base unit may transmits a global time base signal synchronizing the timing of transmission of signals acquired by the plurality of individual wireless transceivers to the base unit in discrete time slots in a single frequency channel. Other examples include data acquisition messages, registration messages, initialization messages, frequency selection command messages, and so forth as described in further detail below.
In yet another aspect of the invention, a wireless, remotely programmable transceiver assembly is provided. The wireless transceiver assembly is adapted to attach to a patch electrode for placement on the surface of a patient""s body, the assembly transmitting signals acquired from the electrode to a base unit. The electrode transceiver assembly includes an amplifier receiving a signal from the electrode and generating an amplified analog signal, a analog to digital converter converting the amplified analog signal into a digital signal, a computing platform such as a microcontroller with a Digital Signal Processor (DSP) function having a memory storing a set of instructions executable by the microcontroller/DSP, a buffer storing digital signals for transmission to the base unit and a wireless transceiver module including an antenna for wireless transmission of the digital signals to the base unit. A frequency generator is provided that is responsive to commands from the microcontroller. The frequency generator generates a signal at frequency at which the wireless transmission from the wireless transceiver assembly to the base unit is to occur. The microcontroller is operative to select a frequency for the wireless transmission in response to control commands received from the base unit.
In still another aspect of the invention, a base unit is provided for a plurality of wireless, programmable transceiver assemblies each adapted to attach to a patch electrode for placement on the surface of a patient""s body. The base unit includes a transceiver module including an antenna for wireless communication in transmit and receive directions between the base unit and the wireless, programmable transceiver assemblies. The wireless communication from the wireless, programmable transceiver assemblies to the base unit occurs in a plurality of discrete time slots in a single frequency channel. The base unit further includes an encoder/decoder coupled to the antenna, a microcontroller and a memory. The microcontroller performs error correction on signals from the encoder/decoder and executes initialization and transceiver management and command routines.
The base unit further includes a demultiplexer demultiplexing received data from the plurality of wireless transceiver assemblies in the plurality of discrete time slots. A digital to analog converter converts the received, demultiplexed digital signals into analog signal. An interface supplies the analog signals to a monitor for display. Preferably, the monitor comprises a conventional, pre-existing ECG monitor. The wireless origin of the supplied analog signals is transparent to the ECG monitor.
These and still other aspects and features of the invention will be more apparent from the following detailed description of a presently preferred embodiment. In this specification, the terms xe2x80x9cwireless transceiverxe2x80x9d and xe2x80x9cprogrammable wireless transceiverxe2x80x9d are meant to refer to the wireless electrode transceiver assembly as a unit, as distinguished from the actual transceiver module within the assembly, unless the context clearly indicates otherwise.